Field of the Invention
The present invention relates to flexible substrates and methods used in the manufacture of flexible substrates.
Technical Background
Flexible substrates can be used in a variety of applications including electronic devices, such as, for example, light emitting displays. In such applications, flexible substrates can be subjected to tensile, compressive, and shear stresses during manufacture, handling, and operation that can result in device failure or a reduction in the lifetime of a device. The mechanical requirements and thus, the selection and/or manufacture of appropriate substrate materials, can vary depending on the intended application. Several factors typically considered in evaluating substrate materials include: mechanical durability, process compatibility, weight, bend radius, thermal capability, surface roughness, transparency, electrical properties, and cost.
Various materials have been used in the manufacture of flexible substrates and devices. Metal substrates, such as, for example, stainless steels, typically exhibit properties, such as, for example, surface roughness, non-transparency, and conductivity, that are incompatible with at least some light emitting display devices. Similarly, thermoplastic substrates, such as, for example, polyethylene naphthalate, polyethersulfone, polycarbonate, and polyimide, can exhibit oxygen and water barrier properties, coefficients of thermal expansion, thermo-mechanical stability, thermal limitations, and chemical durability properties that are incompatible with at least some light emitting display devices. While inorganic film coatings can be employed to alter the barrier properties of thermoplastic substrates, these thin films are typically brittle and are prone to cracking, thus resulting in permeability and/or device failure.
Substrates comprised of glass materials have traditionally been selected based on available materials and extrinsic properties such as, for example, thickness. The glass materials typically selected can exhibit poor mechanical stability as a result of brittleness and/or poor mechanical durability that are not sufficient to withstand the device manufacturing process and/or use in the final application.
The size and durability requirements for electronic devices are continuously increasing. Thus, there is a need to address dimensional stability, coefficients of thermal expansion, toughness, transparency, thermal capability, barrier and hermetic properties, and other properties of flexible substrates related to use in electronic devices. These needs and other needs are satisfied by the composition and methods of the present invention.